public class Tuple<A,B> {
  public A fst;
  public B snd;
  public Tuple(A a, B b) {
    fst = a;
    snd = b;
  }
  public A getFirst() {return fst; }
  public B getSecond() {return snd; }
  public void setFirst(A a) {fst = a; }
  public void setSecond(B b) {snd = b; }
}
